Parallel vices of that kind, with a quadrangular guide means, in accordance with DIN 5115, are known in a wide range of constructions. The housing generally has an opening of rectangular cross-section, the inner surfaces defining that opening forming the guide tracks for the slider which is also of rectangular cross-section. The slider itself is generally of a downwardly open, substantially U-shaped cross-section, while disposed in the interior of the slider is a screw spindle which is mounted rotatably but axially immovably at the forward end of the slider. In addition, a nut is connected to the base plate of the housing, the nut engaging from below into the slider while the screw spindle can be screwed in the nut. The maximum width of clamping of the known parallel vices is limited by the length of the slider and is always shorter than the slider itself as, when the vice is in a completely open condition, the slider must still engage over a sufficient length into the guide means of the housing. In most of the known parallel vices, the housing comprises a bottom portion and a top portion so that the guide tracks of the quandrangular guide means, which are provided in the housing, can be easily machined. However the production of the two housing portions and precise machining of the connecting surfaces involves an additional manufacturing cost. There are however also vices in which the housing is of a onepart construction but in that case the guide surfaces of the guide means are difficult to machine, particularly when a higher degree of accuracy in respect of the vice is required. The slider which is of a cross-section that is open at one side also has a low level of stiffness.
The invention is based on the problem of providing a forwardly opening parallel vice of the kind set forth in the opening part of this specification, which is easy to produce and which can be used like a conventional vice, in which however if necessary the width of clamping can be increased as desired beyond the normal displaceability of the slider. The invention further seeks to provide that the slider enjoys increased stiffness.
The underlying problem of the invention is solved in that the slider is of square cross-section and the axis of the screw spindle is arranged precisely in the center of the square cross-section, wherein the guide surfaces which are provided at the four sides of the slider and the guide tracks of the housing, which co-operate with the guide surfaces, form tangents to a common circle, the center point of which is the axis of the screw spindle.
In normal operation the novel parallel vice can be used like a conventional, forwardly opening parallel vice. If however the vice is to be used for clamping workpieces whose dimensions are greater than the maximum width of clamping of the vice, then the slider can be drawn completely out of the guide means of the housing, turned through 90.degree. about the axis of the screw spindle and refitted into the guide means in the housing. By virtue of the square cross-section, the slider is then also guided precisely in the housing, in that position. However the movable clamping jaw is now no longer disposed opposite to the fixed clamping jaw but at one side of the housing. The workpiece to be clamped can then be put on to the workpiece beside the housing and can be brought to bear against a support means or co-operating jaw member which is fixed to or can be fixed to the workbench. The workpiece can now be clamped fast between the movable clamping jaw and the support means or the co-operating jaw by means of the movable clamping jaw which projects beyond the side surface of the housing.
The slider desirably is of a cross-section which is closed on all sides and which is only open rearwardly. By virtue of that arrangement the slider has optimum bending and torsional strength in any direction. In addition the screw spindle, in its operative position, is completely surrounded by the slider or the housing and is thus protected from fouling and damage.